The present invention relates to a plug connector which is used in connection with a plug for a headphone combined with a microphone (hereinafter, such a plug is referred to as “microphone-equipped headphone plug”) in an audio apparatus, and particularly to a plug connector having a function of detecting insertion/extraction of a plug.
FIG. 9 is a circuit diagram showing the configuration of an audio apparatus including a plug connector 100 of the related art. The plug connector 100 includes a jack portion 110 into which a pin 10 of a microphone-equipped headphone plug 1 is to be inserted.
In the side surface of the pin 10, speaker contact portions 11L, 11R, a ground contact portion 12, and a microphone contact portion 13 are sequentially formed with starting from the tip end of the pin along the direction of insertion into the jack portion 110. Insulating portions 14 are interposed in spaces between the contact portions 11L, 11R, 12, 1312 respectively. Here, the speaker contact portions 11L, 11R are connected to L- and R-channel speakers of a headphone, respectively. The ground contact portion 12 is connected to ground terminals of the speakers and microphone of the headphone. The microphone contact portion 13 is connected to the microphone of the headphone.
The jack portion 110 has spring contacts 111, 112, 113, 114. In a state where the pin 10 is inserted in the jack portion 110, the contacts 111, 112, 113, 114 are in contact with the contact portions 11L, 11R, 12, 13 of the pin 10, respectively. The contact 111 cooperates with a contact 115 to constitute a mechanical switch 116.
A headphone semiconductor integrated circuit 200 generates an audio signal which is to be supplied to the headphone connected to the plug connector 100, and receives and processes an audio signal which is to be supplied from the headphone. In FIG. 9, among components constituting the headphone semiconductor integrated circuit 200, only components related to the function of the plug connector 100 are illustrated. As shown in FIG. 9, the headphone semiconductor integrated circuit 200 has control circuits 201, 202, potential detectors 211, 212, speaker amplifiers 220L, 220R, a microphone amplifier 230, and a bias circuit 240. The headphone semiconductor integrated circuit 200 further has terminals DETIN, HPOUTL, HPOUTR, MICIN, MICDET, MICBIAS.
The contact 115 of the jack portion 110 is connected to the terminal DETIN, and connected also to a power supply VCC through a resistor R1. The contact 111 is connected to the terminal HPOUTL, and grounded through a resistor R2. The contact 112 is connected to the terminal HPOUTR. The contact 113 is grounded. The contact 114 is connected to the terminal MICIN through a capacitor C. The contact 114 is further connected to the terminal MICDET, and also to the terminal MICBIAS through a resistor R3.
In the headphone semiconductor integrated circuit 200, the speaker amplifiers 220L, 220R are circuits which output signals for driving the two or L- and R-channel speakers of the headphone connected to the microphone-equipped headphone plug 1, from the terminals HPOUTL, HPOUTR, respectively. The microphone amplifier 230 amplifies an input signal which is supplied through the terminal MICIN. The bias circuit 240 outputs a bias voltage which is to be applied to the microphone of the headphone connected the microphone-equipped headphone plug 1. The potential detector 211 is a circuit for detecting whether the potential of the terminal DETIN is equal to or higher than a predetermined threshold or not. The control circuit 201 detects insertion/extraction of the pin 10 of the microphone-equipped headphone plug 1 into/from the jack portion 110, based on the result of the detection of the potential detector 211, and controls various portions based on a result of the insertion/extraction detection. The potential detector 212 is a circuit for detecting whether the potential of the terminal MICDET is lower than a predetermined threshold or not. Based on a result of the detection of the potential detector 212, the control circuit 202 determines whether the headphone is equipped with a microphone or not, or whether a switch which is connected in parallel to the microphone of the microphone-equipped headphone is turned ON/OFF.
FIG. 9 shows a state where the pin 10 of the microphone-equipped headphone plug 1 is inserted in the jack portion 110. In the state, the contact 111 is separated from the contact 115 by the speaker contact portion 11L at the tip end of the pin 10, so that the mechanical switch 116 is turned OFF and the power supply voltage VCC is applied to the terminal DETIN. In this case, the potential detector 211 detects that the potential of the terminal DETIN is higher than the threshold. As a result, the control circuit 201 deems that the pin 10 is inserted in the jack portion 110, and applies the power supply voltage to circuits such as the speaker amplifiers 220L, 220R, the microphone amplifier 230, and the bias circuit 240, thereby causing the circuits to operate.
FIG. 10 shows a state where the pin 10 of the microphone-equipped headphone plug 1 is extracted from the jack portion 110. In the state, the pin 10 is separated from the contact 111, and therefore the contact 111 butts against the contact 115, so that the mechanical switch 116 is turned ON and a voltage which is obtained by dividing the power supply voltage VCC with the resistors R1, R2 is applied to the terminal DETIN. In this case, the potential detector 211 detects that the potential of the terminal DETIN is lower than the threshold. As a result, the control circuit 201 deems that the pin 10 is extracted from the jack portion 110, and controls circuits such as the speaker amplifiers 220L, 220R, the microphone amplifier 230, and the bias circuit 240 so as to stop their operations.
Techniques for detecting insertion/extraction of a plug of this kind are disclosed in, for example, Japanese Patent No. 3,407,622 and JP-A-2008-294803.
In the above-described plug connector 100 of the related art, the mechanical switch 116 is required for detecting insertion/extraction of the pin 10, and hence there is a problem in that the plug connector cannot be applied to a jack portion not having the mechanical switch 116.
The plug connector 100 of the related art has a further problem in that there is a case where, during the process of extracting the pin 10 of the microphone-equipped headphone plug 1 from the jack portion 110, a noise is emitted from the speakers of the headphone. Hereinafter, the problem will be described with reference to FIG. 11.
FIG. 11 exemplarily shows a state where the pin 10 is slightly extracted from the jack portion 110, and the contact 114 is in contact with the ground contact portion 12. In FIG. 11, wirings interposed between the contact portions 13, 12, 11R, 11L, and the microphone M, ground wire, left and right speakers SPL, SPR of the headphone (mainly wiring in cables connecting the microphone-equipped headphone plug 1 with the headphone speakers and the microphone M) are indicated by broken lines. In the example, in the state where the contact 114 is in contact with the ground contact portion 12, the speaker contact portion 11L at the tip end of the pin 10 remains to butt against the contact 111, the contact 111 is separated from the contact 115, and the mechanical switch 116 is turned OFF. Depending on the configuration of the jack portion 110, such a state may occur when the plug 1 is extracted.
In this state, since the mechanical switch 116 is turned OFF, the power supply voltage VCC is applied to the terminal DETIN. Therefore, the control circuit 201 continues to allow circuits such as the speaker amplifiers 220L, 220R, the microphone amplifier 230, and the bias circuit 240 to operate. Consequently, a current flows from the output terminal of the bias circuit 240 into the ground contact portion 12 through the resistor R3. A part of the current which flows into the ground contact portion 12 flows to the speaker SPR of the headphone through wirings interposed between the ground contact portion 12 and the speaker SPR, and then flows from the speaker SPR into the ground wire through the speaker contact portion 11R and the contact 113. The remaining part of the current which flows into the ground contact portion 12 flows to the speaker SPL of the headphone through wirings interposed between the ground contact portion 12 and the speaker SPL, and then flows from the speaker SPL into the speaker contact portion 11L. The current which flows into the speaker contact portion 11L thereafter flows into the output terminal of the speaker amplifier 220R through the contact 112 and the terminal HPOUTR, or flows into the output terminal of the speaker amplifier 220L through the contact 111 and the terminal HPOUTL, or flows from the contact 111 into the ground wire through the resistor R2.
When the pin 10 is further extracted from the jack portion 110, thereafter, the speaker contact portion 11L at the tip end of the pin 10 is separated from the contact 111, and the mechanical switch 116 is turned ON. This causes the control circuit 201 to stop the operation of the bias circuit 240. As a result, the current output from the output terminal of the bias circuit 240 is interrupted, and also the current supply to the speakers SPL, SPR is cut off.
As described above, the plug connector 100 of the related art has the problem in that, during the process of extracting the pin 10 from the jack portion 110, a pulsed current flows to the speakers SPL, SPR of the headphone, and a noise is sometimes emitted from the speakers.